Study of Intramolecular Cyclization of Organic etero-Containing Enynes Catalyzed by Ruthenium Metal Complexes
Date Issued
2009
Date
2009
Author(s)
Chiang, Pei-Yun
Abstract
In this thesis, we investigated versatile reactivities of half-sandwiched ruthenium complexes with hetero-atom containing organic compounds. A series of ruthenium vinylidene and acetylide complexes containing amine, aniline, oxygen, and pyridyl groups have prepared. We studied the intramolecular cyclization of organic 1,7-enynes containing heteroatom catalyzed by ruthenium to form indole products via vinylidene intemediates [[Ru]=C=CH(Ph)N(CH2CHCR1R2)2][PF6] ([Ru] = CpRuL2; 4a, L = PPh3, R1 = R2 = H; 4b, L = PPh3, R1 = CH3, R2 = H; 4b’, L = 1/2 dppe, R1 = CH3, R2 = H; 8c’, L = 1/2 dppe, R1 = R2 = CH3). Complex 4b’ undergoes a 5-endo-dig cyclization followed by a [3,3]-sigmatropic rearrangement to give complex [[Ru]{=C(C14H19N)}][PF6] 7b’. Further reaction in chlorinated solvent resulting in formation of the indole product 6b via a 1,2-hydrogen migration furnishes a catalytic cycle. This cyclization reaction provides a direct approach to substituted indole compound under mild condition and gives good diasetereoselectivity. Only (SR/RS) form products are obtained without observing the other probable (SS/RR) isomers. Complexes 4a and 4c’ can undergo a resembling transformation to form indoles 6a and 6c, respectively. The cyclization is also influenced by the steric effect and electronic effect in the cases of [Cp(PPh3)2Ru=C=CH(Ph)N- (CH2CHCMe2)2][PF6] (4c) and [[Ru]=C=CH(Ph)NHCOCH3][BF4] (10) where no cyclization product is formed. urther extention of the N-containing 1,7-enynes gives a propargylic alcohol pyridine 12, where the N-atom is at the C5-position on the phenyl ring. Reaction of Cp(PPh3)2RuCl with 12 affords a cyclic indolizinone complex [[Ru]{–C(C7H5ON)}][PF6] (13) in a mixture of methanol and THF. Dramatically, using CH2Cl2 as a solvent, treatment of 12 with [Ru]Cl in the presence of KPF6 yields three new products, 14, 15 and 16, in a ratio of 2.4 : 1 : 1.6. Complex [CpPPh3Ruη²-HC≡CC(=O)(C5H4N)][PF6] (14)s an alkynyl-N-coordinating intermediate with chelating C,N ligand. The oxidation via b-hydride transfer from ruthenium-alkoxide generates ruthenium-hydride and the ketone pyridine ligand. Complex 15 is a six-membered aza-metallacyclic phosphine-additionompound with one coordinating PPh3 and one N,C-chelating C(H)=C(PPh3)C(=O)(C5H4N) ligand. Complex 16 is a five-membered azametallacyclic cationic complex with one coordinating PPh3 and one N,C-chelating C(=CH(PPh3))C(=O)(C5H4N) ligand. The formation of 16 and 15 are from the nucleophilic addition of PPh3 to Ca and Cb of coordinated alkyne of complex 14, respectively. Alternatively, the hydroxyl group of 12 is protected by a TBS group to yield 17 and further reaction of 17 with [Ru]Cl in the presence of KPF6 in CH2Cl2 also leads to formation a mixture of phosphine-addition products 18 and 19 in a ratio of 1:4. series of oxygen-containing acetylide and vinylidene complexes [[Ru]=C=CH(Ph)OCH2CHCR2][PF6] ([Ru] = CpRuL2; 23a, L = PPh3, R = H; 23b, L =PPh3, R = CH3; 23a’, L = 1/2 dppe, R = H; 23b’, L = 1/2 dppe, R = CH3) are prepared.omplex 23a transforms to an oxycarbene complex 24 by removing the allyl group under acidic condition, but, the vinylidene complex 23a’ would not give the cyclicarbene complex under the same reaction condition. Other vinylidene complexes [[Ru]=C=C(R)CH2COOR’][PF6] (29) are synthesis by alkylation reactions of alkyl halides with two acetylide complexes Cp(PPh3)2RuC≡CR (28, R = Me; 28’, R = Ph).Treatment of various complexes 29 with n-Bu4NOH yields corresponding ruthenium furyl complexes 31a (R = Me, R’= Et) and 31b (R = Me, R’= CH2CF3).
Subjects
ruthenium
catalysis
indoles
cyclization
rearrangement
indolizinone
PPh3 addition
furan
Type
thesis
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